This study investigates patterns of connectors in L2 academic writing and the effects of instruction on students’ output in the use of connectors. Specifically, the current study examines 1) how ESL learners’ writing proficiency relates to sentence connectors, 2) whether different levels of learners shows distinctive patterns in the use of sentence connectors, and 3) different approaches in grammar instruction (structured input approach, and text-based approach) facilitates the appropriate use of connectors. Students’ writing samples from the placement test at an academic English program was analyzed. The results showed no meaningful differences in the use of connectors among participants whose level of proficiency differ. However, surprisingly, learners with low level of proficiency tended to overuse the connectors. Finally, the instruction effects of sentences connectors were not meaningfully powerful. Nevertheless, this study was informative in that it suggests students’ needs in specific types of connectors.